The design and methods for MRFIT have been reported in detail
elsewhere (MRFIT 1977 JChronDis, MRFIT 1981 MonoPrevMed, MRFIT 1982
JAMA). Briefly, MRFIT was a randomized controlled trial on the
primary prevention of CHD mortality among men ages 35 to 57 years
who were at increased risk but without definitive clinical evidence
of CHD (coronary heart disease) at baseline. From 1973 to 1975, 22 
clinical centers in 18 cities across the U.S. screened 361,662 men 
for participation.

Men were excluded at Screen 1 if their cigarette smoking, serum
cholesterol, and blood pressure measurements did not place them in
the upper 15% (later upper 10%) of a risk score distribution (based
on the Framingham Study), or if they had a history of
hospitalization for heart attack, diabetes mellitus requiring
medication, expected geographic mobility, serum cholesterol 350
mg/dL or higher, or diastolic blood pressure 115 mm Hg or higher
(MRFIT 1982 JAMA). Screen 2 on average 44 days later excluded men
for obesity, angina pectoris, history or ECG evidence of myocardial
infarction, untreated symptomatic diabetes, diets incompatible with
the MRFIT food pattern, treatment with certain medications
(e.g. hypoglycemic or lipid-lowering agents), illnesses or
disabilities likely to restrict full trial participation, and
diastolic blood pressure 120 mm Hg or higher (MRFIT 1982 JAMA).

At Screen 3, informed consent was obtained and the intervention was
randomly assigned (stratified by clinic). The randomized
intervention was comprised of dietary counseling to lower
cholesterol, smoking cessation counseling, and stepped-care
hypertension medication (Caggiula 1981 PrevMed, Hughes 1981 PrevMed,
Cohen 1981 PrevMed) (called "special intervention"). The placebo
group (called "usual care") remained under the care of their primary
physician.

On or about each anniversary of randomization, participants returned
to their clinical center for an examination by a MRFIT physician and
to complete behavioral, medical history, and 24 hour dietary recall
questionnaires. The men were requested to arrive for their annual
visits in the morning after an overnight fast.  Fasting serum
samples were collected for each participant and were analyzed at a
central laboratory at the Institute of Medical Sciences, San
Francisco, CA (Widdowson 1986 CCT) for total serum
cholesterol. Blood pressure was measured according to a standard
protocol by certified personnel (Cohen 1981 PrevMed). Systolic and
diastolic readings were recorded from the first and fifth Korotkoff
phase readings obtained with a random-zero sphygmomanometer while
the participant was seated. Blood pressure at baseline was defined
as the average of 2 measurements at Screen 2 and two measurements at
Screen 3.

Age at randomization was determined from the participant's recorded
birthdate. Race (African-American=2, American Indian=5,
Asian-American=3, Caucasian=1, Spanish American=4, Other=6) was
determined by self-report at Screen 1.  Disrobed height and weight
were recorded at Screen 2; we use Body Mass Index (BMI)
 in kg/m^2. Alcohol use was determined at Screen 2 by self-report
of the number of drinks (beer, wine, whiskey, or other liquor)
usually consumed per week. Cigarette use as self-reported number
smoked per day was recorded at Screen 1. Randomization group is
coded as 1 for special intervention and 2 for usual care. Marital
status is coded as 1=never married, 2=separated, 3=divorced, 4=widowed, 
and 5=married.